The present invention relates to rocker support assemblies and breather assemblies for internal combustion engines.
Combustion gases produced in the combustion chamber of an internal combustion engine are commonly forced under pressure to flow past the piston of the engine and into the engine""s crankcase. Such gas is called xe2x80x9cblow-byxe2x80x9d gas, and usually consists at least partially of an air/oil mist. The reciprocation of the piston typically causes pressure fluctuations in the crankcase, causing the air/oil mist in the crankcase to be routed through an air cleaner having an air filter and back to the intake of the carburetor. It is undesirable to have oil in the combustion chamber because this leads to accumulations of oil in the valves and combustion chamber which may interfere with the operation of the engine. Also, the air filter in the air cleaner must be replaced frequently due to larger amounts of oil suspended in the air passing through the air cleaner, adding maintenance expense.
To alleviate this problem, it is customary in a four cycle engine to provide a breather system for separating the oil from the air/oil mist prior to recycling the air through the air cleaner and the carburetor. In a typical breather system as shown in U.S. Pat. No. 4,169,432, the oil mist in the crankcase is subjected to positive pressure when the piston travels in a downstroke, and the oil mist is forced through a breather passage containing a check or breather valve to an oil separation chamber where the oil mist is separated from the gas. On the upstroke of the piston, the pressure in the crankcase changes from positive to negative and the separated oil is drawn back into the crankcase through a return passage.
The present invention provides a rocker support assembly for an internal combustion engine of a motor vehicle (e.g., a motorcycle). The rocker support assembly includes a pair of rockers and a breather assembly including a breather housing that is advantageously positioned between the rockers. Such positioning of the breather housing provides a compact, low profile rocker box. Furthermore, by properly positioning the rockers, the breather housing can be positioned in the middle of the rocker box to enhance the efficiency of the breather system.
In one embodiment, a cylinder head for a motorcycle engine includes a lower surface adapted to be coupled to a cylinder, an upper surface adapted to be coupled to a rocker box and defining a plane, and a side connected between the upper surface and the lower surface. The head also includes a breather inlet extending into the upper surface, an intermediate passage extending into the upper surface, and a breather channel connecting the inlet and the intermediate passage, the breather channel lying in a plane that is generally parallel to the plane of the upper surface. The head also includes a breather passage extending into the side of the head and connected to the intermediate passage, the breather passage having a longitudinal axis that is generally parallel to the plane of the upper surface. A line connecting the inlet and the intermediate passage is at an obtuse angle to the longitudinal axis of the breather passage. The breather passage has a length, and the breather channel has a length greater than the length of the breather passage. Finally, the intermediate passage has a longitudinal axis that is generally perpendicular to the plane of the upper surface.
In another aspect of the invention, the head includes two threaded openings in the upper surface adapted to receive breather bolts and defining a line connecting the threaded openings, and a breather channel intersecting the line. The breather channel includes an inlet that intersects the line. The line has a length and the breather channel has a length greater than half of the length of the line.
In another aspect, the head includes two generally circular valve openings adapted to receive valves, the valve openings having centers that define a first reference line connecting the centers. The breather channel intersects a second reference line perpendicularly bisecting the first reference line. The first reference line has a length and the breather channel has a length greater than half of the length of the first reference line.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.